MEMS Devices Including MEMS Dies and Connectors Thereto

ABSTRACT

An embodiment is MEMS device including a first MEMS die having a first cavity at a first pressure, a second MEMS die having a second cavity at a second pressure, the second pressure being different from the first pressure, and a molding material surrounding the first MEMS die and the second MEMS die, the molding material having a first surface over the first and the second MEMS dies. The device further includes a first set of electrical connectors in the molding material, each of the first set of electrical connectors coupling at least one of the first and the second MEMS dies to the first surface of the molding material, and a second set of electrical connectors over the first surface of the molding material, each of the second set of electrical connectors being coupled to at least one of the first set of electrical connectors.

This application is a divisional of U.S. patent application Ser. No.15/160,884, filed May 20, 2016, which is a divisional of U.S. patentapplication Ser. No. 14/157,273, filed Jan. 16, 2014, now U.S. Pat. No.9,352,956, issued on May 31, 2016, entitled “MEMS Devices and Methodsfor Forming Same.” These applications are hereby incorporated herein byreference.

BACKGROUND

Microelectromechanical systems (“MEMS”) are becoming increasinglypopular, particularly as such devices are miniaturized and areintegrated into integrated circuit manufacturing processes. MEMS devicesintroduce their own unique requirements into the integration process,however. Electrically interconnecting MEMS devices is an area of uniquechallenges. In particular, integrating MEMS pressure sensor devices,MEMS motion sensor devices, and MEMS gyroscope sensor devices into thesame integrated circuit manufacturing process has posed challenges.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A through 1H illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device in accordance with someembodiments.

FIGS. 2A through 2I illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device in accordance with someembodiments.

FIGS. 3A through 3F illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device in accordance with someembodiments.

FIG. 4 illustrates a cross-sectional view of a MEMS device in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments will be described with respect to a specific context, namelya MEMS device that can integrate at least two known good dies of anapplication-specific integrated circuit (ASIC) die, a high pressure die,a high vacuum (low pressure) die, and a pressure sensor die. Otherembodiments may also be applied, however, to other MEMS devices havingknown good dies side-by-side or stacked.

FIGS. 1A through 1H illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device die 550 in accordance with someembodiments. With reference now to FIG. 1, there is illustrated a MEMSwafer 100. The MEMS wafer 100 includes a substrate 102 and a dielectriclayer 104 on a surface of the substrate 102. The substrate 102 may beformed of silicon, silicon germanium, silicon carbide or the like. Thesubstrate 102 may be formed of low resistive silicon. Alternatively, thesubstrate 102 may be a silicon-on-insulator (SOI) substrate. The SOIsubstrate may comprise a layer of a semiconductor material (e.g.,silicon, germanium and the like) formed over an insulator layer (e.g.,buried oxide and the like), which is formed in a silicon substrate. Inaddition, other substrates that may be used include multi-layeredsubstrates, gradient substrates, hybrid orientation substrates, thelike, or a combination thereof.

The dielectric layer 104 is formed on a top surface of the substrate102. The dielectric layer 104 may comprise one or more suitabledielectric materials such as silicon oxide, silicon nitride, low-kdielectrics such as carbon doped oxides, extremely low-k dielectricssuch as porous carbon doped silicon dioxide, a polymer such aspolyimide, the like, or a combination thereof. The dielectric layer 104may be deposited over substrate 102 using, for example, spinning,chemical vapor disposition (CVD), plasma enhanced chemical vapordeposition (PECVD), low pressure CVD (LPCVD), the like, or a combinationthereof. In some embodiments, the dielectric layer 104 may be a releaselayer and released (i.e., removed) in subsequent process steps in orderto form MEMS structures; therefore, dielectric layer 104 may also bereferred to as sacrificial (SAC) dielectric layer 104.

One or more polysilicon layers 106 may be formed throughout thedielectric layer 104. For example, portions of the polysilicon layer 106may be used as electrical routing, some portions of the polysiliconlayer 106 may act as mechanical structure, or some portions of thepolysilicon layer 106 may act as mechanical bumps to limit the motion ofmoving elements in MEMS wafer 100, or as anti-stiction bumps. In someembodiments, portions of the polysilicon layer 106 may be used as avapor hydrogen-fluoride (vapor HF) etch stop layer in subsequent processsteps. In other embodiments, the layer 114 may be formed of a differentmaterial in lieu of polysilicon such as SiGe, single crystal silicon(e.g., by using a silicon-on-insulator wafer as a starting material), orthe like.

A MEMS layer 108 is formed over the polysilicon layer 106 and thedielectric layer 104. In some embodiments, the MEMS layer 108 is a wafer108 that is attached to the polysilicon layer 106 as illustrated inFIG. 1. The wafer 108 may then be patterned to the form the MEMSstructures 120, 122, and 124 in wafer 108. In some embodiments, the MEMSlayer 108 is formed over the polysilicon layer 106 and the dielectriclayer 104 by a suitable deposition process such as CVD, atomic layerdeposition (ALD), epitaxial growth, or the like. In this embodiment, amask layer (not shown) may be formed over the polysilicon layer 106 andthe dielectric layer 104 and the MEMS layer 108 may be formed inopenings of the mask layer. In some embodiments, the MEMS layer 108 maybe a substrate that is substantially similar to the substrate 102.

The substrate 102 includes openings extending through the substrate 102that are filled with a dielectric material 105. This dielectric material105 is a release layer that is released (i.e., removed) in subsequentprocess steps in order to expose a region 106A of the polysilicon layer106 to an ambient pressure and form a pressure sensor. The region 106Aof polysilicon layer 106 may act as a membrane of the pressure sensordevice in a completed MEMS device die 406 (see FIG. 1H). In thecompleted MEMS device die 406, openings 158 and cavity 220 expose thisregion 106A of polysilicon layer 106 to ambient pressure and the cavity218 exposes this region 106A of polysilicon layer 106 to a sealedpressure. The dielectric material 105 may be formed of the samematerials and by the same processes as the dielectric layer 104described above and the description is not repeated herein.

In some embodiments, the MEMS structure 120 is an accelerometer, theMEMS structure 122 is a gyroscope, and the MEMS structure 124 is apressure sensor. In other embodiments, the MEMS structures 120 and 122may be motion sensors, resonators, or the like. In the illustratedembodiment, the MEMS structures 120, 122, and 124 are formed from thesame MEMS wafer 100. However, in other embodiments, the different MEMSstructures and/or device dies (see 402, 404, and 406 in FIG. 1C) can beformed from different wafers and different processes and laterintegrated together during the molding process (see FIG. 1E).

Bonding material layers 114 (alternatively referred to as bonds 114) areformed over a surface of the MEMS layer 108. The bonding material layers114 may comprise multiple layers 110 and 112 and may be used foreutectic bonding in subsequent process steps to form cavities between acap wafer 200 and the MEMS wafer 100. The bonding material layers 114may be blanket deposited and patterned using for example physical vapordeposition (PVD) and photolithography/etching. The bonding materiallayers 110 may comprise a layer of aluminum copper under a bondingmaterial layer 112 comprising germanium although other metallicmaterials such as gold may also be used. As illustrated in FIG. 1A, someof the layers 110 do not have a layer 112 over them, as these layers 110will be used to form electrical connectors on to provide electricalconnection to adjacent MEMS structure. The bonding material layers 114may or may not be electrically connected to the polysilicon layer 106.

FIG. 1A also illustrates the cap wafer 200 over the MEMS wafer 100. Thecap wafer 200 may or may not be a complementarymetal-oxide-semiconductor (CMOS) wafer, which may or may not haveelectrical circuits (not shown). In particular, the cap wafer 200 mayinclude various active devices such as transistors, capacitors,resistors, diodes, photodiodes, fuses, and the like. The electricalcircuits may be interconnected to perform one or more functions suitablefor a particular application, which may or may not be related to theMEMS structures 120, 122, and 124. FIG. 1A illustrates the cap wafer 200as having a substrate 202 and cavities 204 and 206 formed in thesubstrate 202. However, in some embodiments, the cap wafer 200 may alsoinclude dielectric layers, conductive lines and vias for electricalrouting. The substrate 202 may be a substrate that is substantiallysimilar to the substrate 102 and the description is not repeated herein.

The cavities 206 formed in the cap wafer 200 may function as sealedcavities for a motion sensor, a gyroscope, an accelerometer, and/or apressure sensor after the cap wafer 200 is bonded to the MEMS wafer 100.The cavities 204 are formed between adjacent cavities 206 and arealigned over the bonding material layers 110 to be used as bond pads forelectrical connectors to prevent the cap wafer 200 from being bonded tothese bonding material layers 110.

FIG. 1B illustrates the bonding of the cap wafer 200 to the MEMS wafer100 and grinding the backside of the cap wafer 200 to form caps 210. Thecap wafer 200 may be bonded to the MEMS wafer 100 by eutectic bondingbetween the bonding material layers 112 and 110. The bonding of the capwafer 200 to the MEMS wafer 100 forms three cavities 214, 216, and 218between the cap wafer 200 and the polysilicon layer 106. The pressure ofthe sealed cavities 214, 216, and 218 may be defined by the conditionsof the eutectic bonding process between the cap wafer 200 and the MEMSwafer 100. In an embodiment, each of the caps 210 are bonded by separatebonding processes with each of the bonding processes before performed atdifferent pressures. In some embodiments, the cavities 214, 216, and 218may each have a different pressures, and in other embodiments, they mayeach have a substantially same pressure. In some embodiments, at leastone of the sealed cavities 214, 216, and 218 a low pressure (highvacuum) cavity with a pressure in a range from about 0.1 mbar to about500 mbar, with at least one of the other of the sealed cavities 214,216, and 218 being a high pressure cavity with a pressure in a rangefrom about 2.5 atmospheres (ATM) to about 3.5 ATM. In an embodiment, atleast one of the cavities 214, 216, and 218 has a pressure from about0.1 mbar to about 500 mbar.

The cap wafer 200 is thinned until a desired thickness is achieved andthe backsides of the cavities 204 (see FIG. 1A) are exposed to form theseparate caps 210 over the cavities 214, 216, and 218. The thinningprocess also exposes the bonding material layers 110 aligned with thecavities 204 (see FIG. 1A). These exposed bonding material layers 110will be used as bond pads for subsequently formed electrical connectors130 (see FIG. 1D) and will be referred to as bond pads 111 hereinafter.The thinning process may be implemented by using suitable techniquessuch as grinding, polishing, chemical etching, the like, or acombination thereof. For example, a chemical mechanical polishing (CMP)process may be used to thin the cap wafer 200.

FIG. 1C illustrates the singulation of the MEMS wafer 100 to formseparate MEMS device dies 402, 404, and 406. These separate MEMS devicedies 402, 404, and 406 are then attached to a carrier 302 with anadhesive layer 304 with a CMOS die 500 also attached to the carrier 302with the adhesive layer 304. The CMOS die 500 and the MEMS device dies402, 404, and 406 may be placed on the adhesive layer 304, for example,by a pick-and-place tool. The MEMS wafer 100 may be singulated by asawing process using a die saw, a laser, or the like. In someembodiments, MEMS devices 402, 404, and 406 are tested beforesingulation, and, in other embodiments, they are tested aftersingulation. The types of testing performed depend on the design and/orpurpose of the MEMS device being tested. By testing the MEMS devicesbefore encapsulation (see FIG. 1E), only known good dies are attached tothe carrier 302, and thus, the yield for the subsequently formed MEMSdevice 550 (see FIG. 1H) is improved.

The adhesive layer 304 may be disposed, for example laminated, on thecarrier 302. The adhesive layer 304 may be formed of a glue, such as anultra-violet (UV) glue, or may be a lamination layer formed of a foil.The carrier 302 may be any suitable substrate that provides (duringintermediary operations of the fabrication process) mechanical supportfor the MEMS device dies, the CMOS die, and other structures on top ofthe carrier 302. The carrier 302 may be a wafer including glass, silicon(e.g., a silicon wafer), silicon oxide, metal plate, a ceramic material,or the like.

The CMOS die includes a substrate 502, an interconnect structure 504,and bond pads 510. In an embodiment, the substrate 502 is a part of awafer. The CMOS die 500 may also be referred to as an ASIC die 500. Thesubstrate 502 may be made of a semiconductor material such as silicon,germanium, diamond, or the like. Alternatively, compound materials suchas silicon germanium, silicon carbide, gallium arsenic, indium arsenide,indium phosphide, silicon germanium carbide, gallium arsenic phosphide,gallium indium phosphide, combinations of these, and the like, may alsobe used. Additionally, the substrate 502 may be a SOI substrate.Generally, an SOI substrate includes a layer of a semiconductor materialsuch as epitaxial silicon, germanium, silicon germanium, SOI, silicongermanium on insulator (SGOI), or combinations thereof.

The substrate 502 may include active and passive devices (not shown inFIG. 1C). As one of ordinary skill in the art will recognize, a widevariety of devices such as transistors, capacitors, resistors,combinations of these, and the like may be used to generate thestructural and functional requirements of the design for CMOS die 500.The devices may be formed using any suitable methods.

The interconnect structure 504 is formed over the substrate 502. Theinterconnect structure 504 includes one or more metallization layers 506which are interconnected by vias 508. The metallization layers 506 maybe formed over the active and passive devices and are designed toconnect the various devices to form functional circuitry. Themetallization layers 506 may be formed of alternating layers ofdielectric (e.g., low-k dielectric material) and conductive material(e.g., copper) and may be formed through any suitable process (such asdeposition, damascene, dual damascene, or the like). Although FIG. 1Conly illustrates four metallization layer 506, it is within thecontemplated scope of the present disclosure that there may be more orless metallization layers 506 included in the interconnect structure504.

The bond pads 510 may be formed over and in electrical contact with theinterconnect structure 504 in order to help provide external connectionsto the active and passive devices. The bond pad 510 may be made ofaluminum, an aluminum alloy, copper, a copper alloy, nickel, the like,or a combination thereof. The bond pads 510 may be formed using adeposition process, such as sputtering, to form a layer of material (notshown). Portions of the layer of material may then be removed through asuitable process, such as photolithographic masking and etching, to formthe bond pads 510. However, any other suitable process may be utilizedto form bond pads 510.

FIG. 1D illustrates forming an electrical connector 512 on at least onebond pad 510 and the electrical connectors 130 on the bond pads 111. Theelectrical connectors 512 and 130 may be stud bumps, which are formed bywire bonding on the bond pads 510 and 111, and cutting the bond wirewith a portion of bond wire left attached to the respective bond ball.For example, in FIG. 1D, the electrical connectors 512 and 130 include alower portion and an upper portion, wherein the lower portion may be abond ball formed in the wire bonding, and the upper portion may be theremaining bond wire. The upper portion of the electrical connectors 512and 130 may have a uniform width and a uniform shape that are uniformthroughout the top part, the middle part, and the bottom part of upperportion. The electrical connectors 512 and 130 are formed of non-soldermetallic materials that do not melt at the normal temperatures (forexample, between about 220° C. and about 280° C.) that are used toreflow solder. In some exemplary embodiments, the electrical connectors512 and 130 are made of copper, aluminum, nickel, gold, silver,palladium, the like, or a combination thereof, and may have a compositestructure including a plurality of layers.

In alternative embodiments, the electrical connectors 512 and 130 areformed through electrical plating. In these embodiments, a sacrificiallayer (not shown) is formed over the CMOS die 500 and the MEMS devicedies 402, 404, and 406. A plurality of openings is formed in thesacrificial layer to expose the underlying bond pads 510 and 111. Aplating step is then performed to plate the electrical connectors 512and 130. After the formation of the electrical connectors 512 and 130,the sacrificial layer is then removed.

FIG. 1E illustrates encapsulating the CMOS die 500, the MEMS device dies402, 404, and 406, and the electrical connectors 512 and 130. In someembodiments, the CMOS die 500, the MEMS device dies 402, 404, and 406,and the electrical connectors 512 and 130 are encapsulated by a moldingmaterial 140. The molding material 140 may be molded on the CMOS die500, the MEMS device dies 402, 404, and 406, and the electricalconnectors 512 and 130, for example, using compression molding. In someembodiments, the molding material 140 is made of a molding compound, apolymer, an epoxy, the like, or a combination thereof. A curing step maybe performed to cure the molding material 140, wherein the curing may bea thermal curing, a UV curing, or the like.

In some embodiments, the CMOS die 500, the MEMS device dies 402, 404,and 406, and the electrical connectors 512 and 130 are buried in themolding material 140, and after the curing of the molding material 140,a planarization step, such as a grinding, is performed to remove excessportions of the molding material 140, which excess portions are over topsurfaces of the electrical connectors 512 and 130 as illustrated in FIG.1F. In some embodiments, surfaces 512A of the electrical connectors 512and surfaces 130A of the electrical connectors 130 are exposed, and arelevel with a surface 140A of the molding material 140. The electricalconnectors 512 and 130 may be referred to as through molding vias (TMVs)and will be referred to as TMVs 512 and 130 hereinafter.

FIG. 1G illustrates forming the redistribution lines (RDLs) 520 and 150over the dies and the formation of electrical connectors 524 and 156over the RDLs. The RDL 520 is formed over and is electrically coupled tothe TMV 512 and the RDLs 150 are formed over and are electricallycoupled to the TMVs 130. The RDLs 520 and 150 may be copper, aluminum,tungsten, nickel, the like, or a combination thereof and may be formedusing electroplating or other acceptable methods. Before plating theRDLs 520 and 150, a photo resist (not shown) may be may be formed byspin-on, lamination for a dry-film, or other acceptable methods. Thephoto resist may be patterned to expose the TMVs 512 and 130 andportions of the surface 140A of the molding material 140 usingacceptable photolithography techniques or other acceptable methods.

The RDLs 520 and 150 may include a barrier layer and a seed layer (notshown). The barrier layer is a thin conformal film formed over themolding material 140. The barrier layer may be titanium nitride,tantalum nitride, tungsten nitride, titanium oxynitride, tantalumoxynitride, tungsten oxynitride, titanium, the like, or a combinationthereof. The barrier layer may be deposited using methods such as CVD,PECVD, LPCVD, PVD, ALD, sputtering, or other acceptable methods. Theseed layer is similarly a thin conformal layer formed over the barrierlayer. The seed layer may be the material used to form the RDLs 520 and150 such as copper, aluminum, tungsten, the like, or a combinationthereof. The seed layer may be formed by PVD, ALD, CVD, or otheracceptable methods.

After the RDLs 520 and 150 are formed, the photo resist is removed, forexample, by stripping, and excess seed layer and barrier layer areremoved, for example, by etching using the RDLs as a mask.

A dielectric layer 152 may be formed over the RDLs 520 and 150 and overthe surface 140A of the molding material 140. The dielectric layer 152may be an epoxy, a polyimide, polybenzoxazole (PBO), the like, or acombination thereof. The dielectric layer 152 may be formed using aspin-on technique or other deposition method. Openings (not shown) maybe formed in the dielectric layer 152 to expose portions of the RDLs 520and 150. The openings may be formed using acceptable photolithographytechniques and etching.

After the openings are formed in the dielectric layer 152, under-bumpmetallizations (UBMs) may be formed in those openings. A UBM 522 may beformed over and electrically coupled to the RDL 520 and UBMs 154 may beformed over and electrically coupled to the RDLs 150.

The UBMs 522 and 154 may include one or more layers of conductivematerial. There are many arrangements of materials and layers, such asan arrangement of chrome/chrome-copper alloy/copper/gold, an arrangementof titanium/titanium tungsten/copper, or an arrangement ofcopper/nickel/gold, that are suitable for the formation of the UBMs 522and 154. A photo resist (not shown) may be formed and patterned, so thatsome portions of the dielectric layer 152 are exposed, and some otherportions are covered. A plating process may be performed to plate thematerials and layers on the exposed portions of the dielectric layer 152to form the UBMs 522 and 154. Any suitable materials or layers ofmaterial that may be used for the UBMs 522 and 154 are fully intended tobe included within the scope of the current application. After theplating process, the photo resist may be removed. In some embodiments,the UBMs 522 and 154 may be contact pads 522 and 154.

FIG. 1G illustrates forming electrical connector 524 over andelectrically coupled to the UBMs 522, and forming electrical connectors156 over and electrically coupled to the UBMs 154. In an embodiment, theelectrical connectors 524 and 156 are a ball grid array of solder ballsand/or bumps, such as C4 bumps. In other embodiments, the electricalconnectors 524 and 156 are metal pillars, wherein solder caps are formedon the top surfaces of the metal pillars. In yet other embodiments, theelectrical connectors 524 and 156 are composite bumps comprising copperposts, nickel layers, solder caps, ENIG, ENEPIG, and/or the like.Although not shown in FIG. 1G, the RDL structures allow the electricalconnectors 524 and 156 to be formed outside the lateral edge of theirrespective dies allowing for a fan-out of a ball grid array that mayallow a greater area for the array compared to the active surfaces ofthe dies (see FIG. 2I).

FIG. 1H illustrates removing the carrier 302 and the adhesive layer 304to expose the backside 502B of the CMOS die 500 and the backsides 102Bof the MEMS device dies 402, 404, and 406.

After the carrier 302 and the adhesive layer 304 are removed, thedielectric material 105 may be removed from the openings in the backsideof the MEMS device die 406 to form openings 158. The openings 158 form acavity 220 and expose the cavity 220 to ambient pressure adjacent aregion 106A of the polysilicon layer 106 to form the pressure sensordevice.

The reconfigured MEMS device die 550 formed in FIG. 1H includes a CMOSdie 500 and three MEMS device dies 402, 404, and 406. Each of the threeMEMS device dies 402, 404, and 406 have a sealed cavity (214, 216, and218) and at least one of the three MEMS device dies 402, 404, and 406have a cavity exposed to ambient pressure (220). The pressures of thesealed cavities 214, 216, and 218 can be substantially the same pressureor, because the sealed cavities are formed in separate dies, can havedifferent pressures. In an embodiment, at least one of the sealedcavities 214 and 216 be a low pressure (high vacuum) cavity with apressure in a range from about 0.1 mbar to about 500 mbar, with theother of the sealed cavities 214 and 216 being a high pressure cavitywith a pressure in a range from about 2.5 ATM to about 3.5 ATM. Thesealed cavities 214 and 216 can be formed from differentwafers/processes and the pressure can different depending on theprocesses and/or the requirements for the MEMS device dies. In someembodiments, the cavity 218 can have a low pressure in a range fromabout 0.1 mbar to about 500 mbar and the cavity 220 can have a pressureof about 1 ATM. By singulating and testing the MEMS device dies 402,404, and 406 and the CMOS die 500 before integrating them in to the MEMSdevice die 550, only known good dies are integrated into the MEMS devicedie 550, and thus, the yield for the MEMS device die 550 is improved.Further, by using TMVs rather than through substrate vias (TSVs), thecost of the MEMS device die 550 is further reduced.

FIGS. 2A through 2I illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device die 650 in accordance with someembodiments. This embodiment is similar to the previous embodimentexcept that that the MEMS devices are not singulated into separate diesbut integrated into a single die. Details regarding this embodiment thatare similar to those for the previously described embodiment will not berepeated herein.

FIG. 2A illustrates a MEMS wafer 100 and a cap wafer 200. The structurein FIG. 2A is similar to the structure described above in FIG. 1A andthe description is not repeated herein.

FIG. 2B illustrates the bonding of the cap wafer 200 to the MEMS wafer100 and thinning the cap wafer 200. These steps may be similar to thesteps described above in FIG. 1B and the descriptions are not repeatedherein.

FIG. 2C illustrates attaching a MEMS device die 600 and a CMOS die 500to a carrier 302 using the adhesive film 304. The MEMS device die 600includes the three MEMS devices of the three MEMS device dies 402, 404,and 406 illustrated in FIG. 1C and their respective structures have beenillustrated in FIG. 2C. The structure of FIG. 2C is similar to thestructure of FIG. 1C except that the MEMS devices of the MEMS device die600 in FIG. 2C have not been singulated, and thus, the description ofthe structure is not repeated herein.

FIG. 2D illustrated the formation of electrical connectors 132 over andelectrically coupled to the bond pads 111. The electrical connectors 132are similar to the electrical connectors 130 in FIG. 1D and thedescription will not be repeated herein. In some embodiments, theelectrical connectors 132 are formed to have a top surface below a topsurface of the caps 210. In some embodiments, the bond pads 510 do nothave electrical connectors formed over and electrically coupled to them,while, in other embodiments, electrical connectors are formed over andelectrically coupled to the bond pads 510 (see FIG. 1D).

FIG. 2E illustrates encapsulating the CMOS die 500 and the MEMS devicedie 600 and the electrical connectors 132 with a molding material 140.The encapsulation process may be similar to the process described abovein Figure lE and the description is not repeated herein.

FIG. 2F illustrates thinning the molding material 140. The thinningprocess may be similar to the thinning process described above in FIG.1F and the description is not repeated herein. However, in theillustrated embodiment, the thinning process does not expose the topsurfaces of the electrical connectors 132 or the bond pads 510. In otherembodiments, the top surfaces of the electrical connectors 132 and thebond pads 510 are exposed by the thinning of the molding material 140.

FIG. 2G illustrates patterning the molding material 140 to exposeportions of the electrical connectors 132 and at least one bond pad 510.The bond pad(s) 510 may be exposed in opening(s) 142 and the electricalconnectors 132 may be exposed in openings 144. The openings 142 and 144may be formed using acceptable photolithography techniques and etching,such as a laser etching process.

FIG. 2H illustrates forming the RDL 530 over and electrically coupled tothe bond pad 510 and the RDLs 162 over and electrically coupled to theelectrical connectors 132 with electrical connectors 532 and 164 formedon the RDLs 530 and 162, respectively. The RDLs 530 and 162 may besimilar to the RDLs 150 described above in FIG. 1G and the descriptionis not repeated herein. The electrical connectors 532 and 164 may besimilar to the electrical connectors 524 and 156 described above in FIG.1G and the description is not repeated herein. In some embodiments, theelectrical connectors 532 and 164 are coupled directly to the RDLs 530and 162, respectively, without using a UBM, and, in other embodiments, aUBM is included between the electrical connectors and RDLs.

FIG. 2I illustrates removing the carrier 302 and the adhesive layer 304to expose a backside of the CMOS die 500 and the MEMS device die 600 andforming the openings 158 in the backside of the MEMS device die 600. Thestructure and function of the reconfigured MEMS device die 650 in FIG.2I may be similar to the structure and function of MEMS device die 550in FIG. 1H and the description is not repeated herein. As illustrated inFIG. 2I, the RDL structures allow the electrical connectors 532 and 164to be formed outside the lateral edge of their respective dies allowingfor a fan-out of a ball grid array that may allow a greater area for thearray compared to the active surfaces of the dies

FIGS. 3A through 3F illustrate cross-sectional views of intermediatestages of manufacture of a MEMS device die 900 in accordance with someembodiments. Details regarding this embodiment that are similar to thosefor the previously described embodiments will not be repeated herein.

FIG. 3A illustrates a CMOS wafer 700 including a substrate 702, aninterconnect structure 704, a dielectric layer 714, and bond pads 712.The substrate 702 may be made of a semiconductor material such assilicon, germanium, diamond, or the like. Alternatively, compoundmaterials such as silicon germanium, silicon carbide, gallium arsenic,indium arsenide, indium phosphide, silicon germanium carbide, galliumarsenic phosphide, gallium indium phosphide, combinations of these, andthe like, may also be used. Additionally, the substrate 702 may be a SOIsubstrate. Generally, an SOI substrate includes a layer of asemiconductor material such as epitaxial silicon, germanium, silicongermanium, SOI, SGOI, or combinations thereof.

The substrate 702 may include active and passive devices 706. As one ofordinary skill in the art will recognize, a wide variety of devices 706such as transistors, capacitors, resistors, combinations of these, andthe like may be used to generate the structural and functionalrequirements of the design for the MEMS device die 900. The devices 706may be formed using any suitable methods.

The interconnect structure 704 is formed over the substrate 702. Theinterconnect structure 704 includes one or more metallization layers 708which are interconnected by vias 710. The metallization layers 708 maybe formed over the active and passive devices 706 and are designed toconnect the various devices 706 to form functional circuitry. Themetallization layers 708 may be formed of alternating layers ofdielectric (e.g., low-k dielectric material) and conductive material(e.g., copper) and may be formed through any suitable process (such asdeposition, damascene, dual damascene, or the like). Although FIG. 3Aonly illustrates two metallization layers 708, it is within thecontemplated scope of the present disclosure that there may be more orless metallization layers 708 included in the interconnect structure704.

The bond pads 712 may be formed over and in electrical contact with theinterconnect structure 704 in order to help provide external connectionsto the active and passive devices 706. The bond pads 712 may be made ofaluminum, an aluminum alloy, copper, a copper alloy, nickel, the like,or a combination thereof. The bond pads 712 may be formed using adeposition process, such as sputtering, to form a layer of material (notshown). Portions of the layer of material may then be removed through asuitable process, such as photolithographic masking and etching, to formthe bond pads 712. However, any other suitable process may be utilizedto form bond pads 712.

A dielectric layer 714 may be formed over the bond pads 712 and over theinterconnect structure 704. The dielectric layer 714 may be an epoxy, apolyimide, PBO, the like, or a combination thereof. The dielectric layer714 may be formed using a spin-on technique or other deposition method.

FIG. 3B illustrates attaching a MEMS device die 800 to dielectric layer714 of the CMOS wafer 700. In an embodiment, the MEMS device die 800 isattached using an adhesive film (not shown) such as a glue film. TheMEMS device die 800 may be similar to any one of the MEMS device dies402, 404, and 406 described above and the descriptions will not berepeated herein.

The MEMS device die 800 includes a substrate 802, an interconnectstructure 804 over the substrate 802, a cap 812 forming a cavity 808, aMEMS structure 806 surrounded by the cavity 808, bonding material layers810 bonding the cap 812 to the MEMS structure wafer, and a bonding pad814. In an embodiment, these structures of the MEMS device die 800 aresimilar to the respective structures of the MEMS device dies 402, 404,and 406. In some embodiments, the cap 812 is an ASIC die and may includeactive and passive devices. In some embodiments, the substrate 802 is anASIC die and may include active and passive devices. In the embodimentswherein the cap 812 and/or the substrate 802 are ASIC dies, the size ofthe CMOS wafer 700 may be reduced because some of the active and passivedevices, which were in the CMOS wafer 700, can be included in the cap812 and/or the substrate 802. This can reduce the overall size and costof the MEMS device.

FIG. 3C illustrates the MEMS device die 800 after it has been attachedto the CMOS wafer 700. FIG. 3D illustrates forming the electricalconnectors 820 and 720 over and electrically coupled to the bond pads814 and 712, respectively. The electrical connectors 820 and 720 may besimilar to the electrical connectors 512 and 130 described above in FIG.1D and the description is not repeated herein.

FIG. 3E illustrates encapsulating the MEMS device die 800 and theelectrical connectors 820 and 720 in a molding material 830 and thinningthe molding material 830. The encapsulation process may be similar tothe encapsulation process described above in Figure lE and thedescription is not repeated herein. The thinning process may be similarto the thinning process described above in FIG. 1F and the descriptionis not repeated herein. In some embodiments, the molding material 830 isthinned to have a surface 830A substantially coplanar with a surface820A of the electrical connector 820 and a surface 720A of theelectrical connector 720.

FIG. 3F illustrates forming the RDLs 840A and 840B, the dielectric layer842, the UBMs 844A and 844B, and the electrical connectors 846A and846B. The electrical connector 846A is electrically coupled to theelectrical connector 720 via the UBM 844A and the RDL 840A. Theelectrical connector 846B is electrically coupled to the electricalconnector 820 via the UBM 844B and the RDL 840B. These structures may besimilar to their respective structures described above in FIG. 1G andthe descriptions are not repeated herein. For example, the RDLs 840A and840B may be similar to the RDLs 520 and 150 in FIG. 1G, the dielectriclayer 842 may be similar to the dielectric layer 152 in FIG. 1G, theUBMs 844A and 844B may be similar to the UBMs 522 and 154 in FIG. 1G,and the electrical connectors 846A and 846B may be similar to theelectrical connectors 524 and 156 in FIG. 1G. Further illustrated inFIG. 1G, the CMOS wafer 700 has been thinned by a backside thinningprocess such as a CMP process.

FIG. 4 illustrates a cross-sectional view of a MEMS device die 1000 inaccordance with some embodiments. The MEMS device die 1000 is similar tothe reconfigured MEMS device die 900 except that the reconfigured MEMSdevice die 1000 includes multiple MEMS device dies 800 (800_1, 800_2,and 800_3) on a CMOS wafer 700. Details regarding this embodiment thatare similar to those for the previously described embodiments will notbe repeated herein.

In this embodiment, each of the MEMS device dies 800 includes anelectrical connector 720 (720_1, 720_2, and 720_3) and the CMOS wafer700 has a corresponding electrical connector 820 (820_1, 820_2, and820_3). Each of the electrical connectors 720 and 820 are coupled toelectrical connectors 846A (846A1, 846A2, and 846A3) and 846B (846B1,846B2, and 846B3), respectively.

By having the MEMS device dies formed separately and later integratedinto a reconfigured die, the pressures of the sealed cavities of thevarious MEMS device dies can be substantially the same pressure or theycan have different pressures. For example, one cavity can be at lowpressure (high vacuum), one cavity can be at high pressure, and anothercavity can be at ambient pressure. Further, by singulating and testingthe MEMS device dies and the CMOS die before integrating them in to thereconfigured MEMS device die, only known good dies are integrated intothe reconfigured MEMS device die, and thus, the yield for thereconfigured MEMS device die is improved. In addition, by using TMVsrather than through substrate vias (TSVs), the cost of the reconfiguredMEMS device die is further reduced.

An embodiment is a method including forming a first amicroelectromechanical system (MEMS) die having a first cavity, thefirst cavity having a first pressure, forming a second MEMS die having asecond cavity, the second cavity having a second pressure, the secondpressure being different from the first pressure, and encapsulating thefirst MEMS die and the second MEMS die with a molding material, themolding material having a first surface. The method further includesforming a first set of electrical connectors in the molding material,each of the first set of electrical connectors coupling at least one ofthe first and the second MEMS dies to the first surface of the moldingmaterial, and forming a second set of electrical connectors over thefirst surface of the molding material, each of the second set ofelectrical connectors being coupled to at least one of the first set ofelectrical connectors.

Another embodiment is a method including forming a MEMS wafer, the MEMSwafer having a first MEMS structure, a second MEMS structure, and athird MEMS structure, bonding a cap wafer to the MEMs wafer, the bondingforming a first cavity over the first MEMS structure, a second cavityover the second MEMS structure, and a third cavity over the third MEMSstructure, and singulating the MEMS wafer forming a first MEMS diecomprising the first MEMS structure and the first cavity, a second MEMSdie comprising the second MEMS structure and the second cavity, and athird MEMS die comprising the third MEMS structure and the third cavity.The method further includes attaching the first MEMS die, the secondMEMS die, and the third MEMS die to a carrier substrate, encapsulatingthe first MEMS die, the second MEMS die, and the third MEMS die with amolding material, the molding material extending from the carriersubstrate over the first MEMS die, the second MEMS die, and the thirdMEMS die, and removing the carrier substrate.

A further embodiment is a microelectromechanical systems (MEMS) devicecomprising: a first MEMS die having a first cavity, the first cavityhaving a first pressure, a second MEMS die having a second cavity, thesecond cavity having a second pressure, the second pressure beingdifferent from the first pressure, and a molding material surroundingthe first MEMS die and the second MEMS die, the molding material havinga first surface over the first and the second MEMS dies. The MEMS devicefurther includes a first set of electrical connectors in the moldingmaterial, each of the first set of electrical connectors coupling atleast one of the first and the second MEMS dies to the first surface ofthe molding material, and a second set of electrical connectors over thefirst surface of the molding material, each of the second set ofelectrical connectors being coupled to at least one of the first set ofelectrical connectors.

A further embodiment is a microelectromechanical systems (MEMS) device.The MEMS device includes a first MEMS die having a first substrate and afirst cavity, the first cavity having a first pressure. The MEMS devicealso includes a second MEMS die having a second substrate and a secondcavity, the second cavity having a second pressure, the second pressurebeing different from the first pressure, the first substrate beingphysically separate from the second substrate. The MEMS device alsoincludes a molding material surrounding the first MEMS die and thesecond MEMS die, the molding material having a first surface over thefirst MEMS die and the second MEMS die. The MEMS device also includes asecond set of electrical connectors over the first surface of themolding material. The MEMS device also includes a first set ofelectrical connectors in the molding material, each of the first set ofelectrical connectors coupling at least one of the first MEMS die andthe second MEMS die to one electrical connector of the second set ofelectrical connectors.

A further embodiment is a MEMS device. The MEMS device includes acomplementary metal-oxide-semiconductor (CMOS) wafer, the CMOS wafercomprising an interconnect structure and a dielectric layer overlyingthe interconnect structure. The MEMS device also includes a first MEMSdie over the dielectric layer, the first MEMS die having a firstsubstrate and a first cavity, the first cavity having a first pressure.The MEMS device also includes a second MEMS die over the dielectriclayer, the second MEMS die having a second substrate and a secondcavity, the second cavity having a second pressure, the second pressurebeing different from the first pressure. The MEMS device also includes amolding material surrounding the first MEMS die and the second MEMS die,the molding material having a first surface over the first MEMS die andthe second MEMS die. The MEMS device also includes a first set ofelectrical connectors in the molding material, each of the first set ofelectrical connectors coupling at least one of the first MEMS die andthe second MEMS die to the first surface of the molding material.

A further embodiment is a MEMS device. The MEMS device includes a firstMEMS die having a first cavity, the first cavity having a firstpressure. The MEMS device also includes a second MEMS die having asecond cavity, the second cavity having a second pressure, the secondpressure being different from the first pressure, the first MEMS die andthe second MEMS die overlying a first substrate. The MEMS device alsoincludes a complementary metal-oxide-semiconductor (CMOS) die having asecond substrate, the second substrate being physically separate fromthe first substrate. The MEMS device also includes a molding materialsurrounding the first MEMS die, the second MEMS die, and the CMOS die,the molding material having a first surface over the first MEMS die andthe second MEMS die and the CMOS die. Molding material extends betweenthe first substrate and the second substrate. The MEMS device alsoincludes a first set of electrical connectors in the molding material,each of the first set of electrical connectors coupling at least one ofthe first MEMS die and the second MEMS die to the first surface of themolding material. The MEMS device also includes a second set ofelectrical connectors over the first surface of the molding material,each of the second set of electrical connectors being coupled to atleast one of the first set of electrical connectors.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A microelectromechanical systems (MEMS) device,comprising: a complementary metal-oxide-semiconductor (CMOS) wafer, theCMOS wafer comprising an interconnect structure; a dielectric layeroverlying the interconnect structure; a first MEMS die over thedielectric layer, the first MEMS die having a first substrate and afirst cavity, the first cavity having a first pressure; a second MEMSdie over the dielectric layer, the second MEMS die having a secondsubstrate and a second cavity, the second cavity having a secondpressure, the second pressure being different from the first pressure; amolding material surrounding the first MEMS die and the second MEMS die,the molding material having a first surface over the first MEMS die andthe second MEMS die; and a first set of electrical connectors in themolding material, each of the first set of electrical connectorscoupling at least one of the first MEMS die and the second MEMS die tothe first surface of the molding material.
 2. The MEMS device of claim1, further comprising a second set of electrical connectors over thefirst surface of the molding material, each electrical connector of thefirst set of electrical connectors being coupled to an electricalconnector of the second set of electrical connector.
 3. The MEMS deviceof claim 1, further comprising a third set of electrical connectors inthe molding material, each of the third set of electrical connectorscoupling the CMOS wafer to the first surface of the molding material. 4.The MEMS device of claim 3, wherein an electrical connector of the thirdset of electrical connectors is positioned between the first MEMS dieand the second MEMS die.
 5. The MEMS device of claim 3, furthercomprising a second set of electrical connectors over the first surfaceof the molding material, each electrical connector of the third set ofelectrical connectors being coupled to an electrical connector of thesecond set of electrical connectors.
 6. The MEMS device of claim 3,further comprising a plurality of bond pads disposed in the dielectriclayer, wherein each electrical connector of the third set of electricalconnectors is physically coupled to a bond pad of the plurality of bondpads.
 7. The MEMS device of claim 6, wherein the plurality of bond padsare physically coupled to the interconnect structure.
 8. The MEMS deviceof claim 1, further comprising a third MEMS die having a third cavity,the third cavity having a third pressure, the third pressure beingdifferent from the first pressure and the second pressure, the moldingmaterial surrounding the third MEMS die with the first surface of themolding material being over the third MEMS die.
 9. The MEMS device ofclaim 8, further comprising: a second set of electrical connectorsextending from the dielectric layer to the first surface of the moldingmaterial, wherein a first electrical connector of the second set ofelectrical connectors is disposed between the first MEMS die and thesecond MEMS die, and a second electrical connector of the second set ofelectrical connectors is disposed between the second MEMS die and thethird MEMS die.
 10. A microelectromechanical systems (MEMS) device,comprising: a first MEMS device having a first cavity, the first cavityhaving a first pressure; a second MEMS device having a second cavity,the second cavity having a second pressure, the second pressure beingdifferent from the first pressure, the first MEMS device and the secondMEMS device overlying a first substrate; a complementarymetal-oxide-semiconductor (CMOS) die having a second substrate, thesecond substrate being physically separate from the first substrate; amolding material surrounding the first MEMS device, the second MEMSdevice, and the CMOS die, wherein molding material extends between thefirst substrate and the second substrate, and wherein a first surface ofthe molding material comprises a plurality of recessed regions; a firstset of electrical connectors in the molding material, each of the firstset of electrical connectors coupling at least one of the first MEMSdevice and the second MEMS device to a recessed region of the pluralityof recessed regions; and a second set of electrical connectors over thefirst surface of the molding material, each of the second set ofelectrical connectors being coupled to at least one of the first set ofelectrical connectors.
 11. The MEMS device of claim 10, wherein a firstrecessed region of the plurality of recessed regions is laterallydisposed between the first MEMS device and the second MEMS device. 12.The MEMS device of claim 10, wherein a conductive material extends alongsidewalls and a bottom surface of each of the plurality of recessedregions, and the conductive material extends along the first surface ofthe molding material.
 13. The MEMS device of claim 12, wherein a firstrecessed region of the plurality of recessed regions is disposed overthe CMOS die, wherein a conductive material extends along sidewalls ofthe first recessed region, and wherein the conductive material iselectrically coupled to a bond pad over the CMOS die.
 14. The MEMSdevice of claim 10, wherein the first MEMS device comprises a cap layer,and wherein an upper surface of the cap layer is further from the firstsubstrate than an upper surface of one electrical connector of the firstset of electrical connectors.
 15. A microelectromechanical systems(MEMS) device, comprising: a first substrate; a first MEMS device on thefirst substrate, the first MEMS device having a first cavity; a secondMEMS device on the first substrate, the second MEMS device having asecond cavity; a third MEMS device on the first substrate, the thirdMEMS device having a third cavity, wherein a pressure of the thirdcavity is different than a pressure of the first cavity and a pressureof the second cavity; a complementary metal-oxide-semiconductor (CMOS)die; a molding material extending between the CMOS die and the firstMEMS device, between the first MEMS device and the second MEMS device,and between the second MEMS device and the third MEMS device, wherein afirst surface of the molding material is farthest from the firstsubstrate; a first electrical connector extending between a secondsurface of the molding material and a first bond pad, wherein the secondsurface of the molding material is closer to the first substrate thanthe first surface of the molding material, and the first bond pad isphysically coupled to the first substrate.
 16. The MEMS device accordingto claim 15, wherein the first MEMS device comprises a first cap layerthat partially defines the first cavity, the second MEMS devicecomprises a second cap layer that partially defines the second cavity,and the third MEMS device comprises a third cap layer that partiallydefines the third cavity.
 17. The MEMS device according to claim 16,wherein a surface of the first cap layer that is farthest from the firstsubstrate is further from the first substrate than the second surface ofthe molding material.
 18. The MEMS device according to claim 15, whereina membrane separates the third cavity from ambient air, and the membraneis exposed to the ambient air through an opening in the first substrate.19. The MEMS device according to claim 15, wherein the first electricalconnector is disposed between the second MEMS device and the third MEMSdevice.
 20. The MEMS device according to claim 15, wherein a conductivematerial extends along the first surface of the molding material and thesecond surface of the molding material.